np,nq,nr = map(int,input().split())

def dfs(p ,q, r, l):
    if p < 0 or q < 0 or r < 0:
        return 0
    if p == 1 and q == 0 and r == 0 and l == 0:
        return 1
    if p == 0 and q == 1 and r == 0 and l == 1:
        return 1
    if p == 0 and q == 0 and r == 1 and l == 2:
        return 1
    if l == 0:
        return dfs(p-1, q, r, 1) + dfs(p-1, q, r, 2)
    if l == 1:
        return dfs(p, q-1, r, 0) + dfs(p, q-1, r, 2)
    if l == 2:
        return dfs(p, q, r-1, 0) + dfs(p, q, r-1, 1)

res = dfs(np, nq, nr, 0) + dfs(np, nq, nr, 1) + dfs(np, nq, nr, 2)
print(res)